Hydrostatic penetration device and tool for the same

ABSTRACT

A hydrostatic penetration device for placing on and penetration of the seabed comprises a housing ( 1 ) with a top cover ( 2 ) and a bottom cover ( 3 ), and a through-going vertical tool ( 4 ) for penetration of the seabed. The hydrostatic penetration device comprises at least one low pressure chamber ( 5 ), at least one hydraulic cylinder ( 6 ) with a vertically movable piston and piston rod ( 10 ) which can be driven to upward and downward movement by a flow of pressurised water from the surrounding water to the low pressure chamber ( 5 ), a clamping device ( 8 ) which surrounds the tool ( 4 ) and is connected to the piston rod ( 10 ), and which, during an upward and downward movement of the piston rod can be brought out of and into engagement with the tool respectively, and at least one weight ( 7 ) resting on the piston rod, which weight is vertically movable under the influence of the piston rod ( 10 ) and is arranged to transfer its weight to the clamping device ( 8 ) during a downward movement.

BACKGROUND OF THE INVENTION

The invention concerns a hydrostatic penetration device for placing onand penetration of the seabed, comprising a housing with a top cover anda bottom cover, and a through-going vertical tool for penetration of theseabed. The invention also concerns tools for use with a hydrostaticpenetration device, especially a sampler for core samples, where thetool is a sampler tube.

In addition to being able to be employed together with the said tools,the hydrostatic penetration device will also be able to be employed todrive a test probe down into the seabed, for measurement of, forexample, temperature, mechanical resistance and electrical conductivity.

There are known in the prior art hydrostatic penetration devices in theform of samplers for core samples, e.g. of sediments on the seabed,designed in principle as percussion drill machines, these samplers beingoperated by the pressure difference between a low pressure chamberprovided in the sampler and the ambient hydrostatic pressure. Thestandard known samplers of this type comprise a head to which the toolor the sampler tube is attached and is driven down into the seabed by apiston provided in a piston cylinder which can be connected to thesurrounding water. When the stroke movement is completed, the cylinderis evacuated to the low pressure chamber, and the piston returns to theinitial position, whereupon the cycle process is repeated. The weight ofthe sampler head acts in conjunction with the hydrostatic pressure inorder to provide the energy required to perform the stroke movement orthe drop stroke. Stability problems often arise with such known samplerswhen they are equipped with long sampler tubes, and there can also beproblems in providing sufficient energy if long sampler tubes areemployed.

In order to avoid the drawbacks with known hydrostatic samplers, it hastherefore been proposed that the tool or the sampler tube should bethrough-going in the sampler's head or housing and that the sampler heador housing should be placed on the seabed.

U.S. Pat. No. 3,693,730 describes a sampler in which a housing with anelectromagnetic vibrator is placed on the seabed. A through-going tubeis driven by means of the vibrator down into the seabed, and a drawworksis used to move the vibrator along the pipe.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide a description of ahydrostatic penetration device of the type mentioned in theintroduction, which makes it possible to place the penetration device'shousing on the seabed and for the tool to be through-going in thehousing.

A second object is to provide a hydrostatically operated penetrationdevice wherein the housing itself has a relatively low weight, while theweight which together with the hydrostatic pressure has to contribute tothe drop movement is provided in the form of a weight which is arrangedin the housing and is lifted in a return stroke. If the hydrostaticpenetration device is employed as a sampler, the stability problems ofknown samplers are thereby avoided, while at the same time permittingthe use of sampler tubes of a far greater length than is possible withthe prior art.

A further object of the present invention is that it should be possibleto supply energy as required without the occurrence of any stabilityproblems.

Finally, it is an object of the invention to provide suitable tools foruse with a hydrostatic penetration device according to the invention.

The objects are achieved with a hydrostatic penetration device and toolsof the type mentioned in the introduction which are characterized by thefeatures which are indicated in the claims.

The above-mentioned and other objects are therefore achieved with ahydrostatic penetration device for placing on and penetration of theseabed, comprising a housing with a top cover and a bottom cover, and athrough-going vertical tool for penetration of the seabed, and ischaracterized in that it comprises:

at least one low pressure chamber with a pressure which is lower thanthe pressure in the surrounding water,

at least one hydraulic cylinder with a vertically movable piston andpiston rod which can be driven to upward and downward movement by a flowof pressurized water from the surrounding water to the low pressurechamber, pipes and valves for leading and guiding the said flow ofpressurized water, for controlling the piston's and thereby the pistonrod's movement,

a clamping device which surrounds the tool and is connected to thepiston rod, and which by means of an upward and downward movement of thepiston rod can be brought out of and into engagement with the tool,

at least one vertically movable weight connected to the piston rod,arranged to transfer its weight to the clamping device during adownwardly directed movement,

whereby during an upwardly directed movement the piston rod will liftthe weight and bring the clamping device out of engagement with thetool, thus causing the clamping device to slide upwards along the tool,and during a subsequent downwardly directed movement will bring theclamping device into engagement with the tool, with the result that,under the influence of the weight and force from the piston rod the toolis driven down into the seabed. A new cycle is then initiated where thepiston rod is again moved upwards. The number of cycles which may beperformed will depend on the dimensioning of the low pressure chamber,and will typically amount to 50 cycles.

In an embodiment of the invention the cylinder volume above the pistonin the hydraulic cylinder is permanently connected to the low pressurechamber, during the piston rod's upward and downward movement thecylinder volume below the piston is connected to the surrounding waterand the low pressure chamber respectively, and the housing has at leastone opening to the surrounding water, thus causing the piston rod to beexposed to the pressure in the surrounding water.

In an embodiment of the invention the tool is driven down by impacts,the weight dropping during the introductory part of its downwardlydirected movement, thus causing it to strike the clamping device,driving the tool down with a blow, which is advantageous in sampling ofthe seabed, particularly of hard sediments. In a second embodiment ofthe invention the tool is forced down into the seabed at a constantspeed, which is advantageous when the tool is used to convey a testprobe down into the seabed.

A first tool for use with a hydrostatic penetration device according tothe invention, especially a sampler tube for core samples, ischaracterized according to the invention in that the sampler tube has ahead provided at its lower end with closing jaws hinged to the head witha substantially tubular cross section and toothed gripping surfaceswhich synchronise the closing jaw's movement.

A second tool for use with a hydrostatic penetration device according tothe invention, especially a sampler tube for core samples, ischaracterized according to the invention in that the sampler tube hasprovided at its lower end a head in the form of a valve housing with avalve plate and an arm which constitutes a one-way valve which in anopen position admits water into the sampler tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail in connection withembodiments and as illustrated in the appended drawing.

FIG. 1 is a section through a first embodiment of a hydrostaticpenetration device according to the invention.

FIG. 2a is a more detailed section of the embodiment in FIG. 1.

FIG. 2b is a variant of the embodiment in FIG. 1.

FIG. 2c is a second variant of the embodiment in FIG. 1.

FIG. 3 illustrates a second embodiment of the hydrostatic penetrationdevice according to the invention.

FIG. 4 shows details of the embodiment in FIG. 3.

FIG. 5 shows details in a variant of the embodiment in FIG. 3.

FIG. 6a and FIG. 6b show details in connection with a suction anchoremployed with the present invention and a variant of a valve device forpreventing the stroke movement from being activated before the bottom isreached.

FIG. 7 illustrates the valve gear in the hydrostatic penetration deviceaccording to the invention.

FIG. 8 shows the embodiment in FIG. 7 in more detail.

FIG. 9 illustrates a second variant of the valve gear in the hydrostaticpenetration device according to the present invention.

FIG. 10a and FIG. 10b illustrate the hydrostatic penetration deviceaccording to the present invention employed with a passive test probe.

FIG. 11 illustrates an embodiment of the hydrostatic penetration deviceaccording to the present invention.

FIG. 12a and FIG. 12b illustrate a preferred embodiment of thehydrostatic penetration device according to the present invention.

FIG. 13 illustrates a further embodiment of the hydrostatic penetrationdevice according to the present invention, with the piston rod in theupper position.

FIG. 14 illustrates the hydrostatic penetration device in FIG. 13 withthe piston rod in the lower position.

FIG. 15 illustrates an embodiment of a first tool for use in thehydrostatic penetration device according to the present invention.

FIG. 16 illustrates an embodiment of a second tool for use in ahydrostatic penetration device according to the present invention.

FIG. 17 illustrates a double tower consisting of a shaft or a course fora hydrostatic sampler and a course for a tool for a test probe formeasuring mechanical and/or electrical resistance together withtemperature in the seabed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a section through a hydrostatic penetration device for placingon and penetration of the seabed, especially a hydrostatic sampler,according to the present invention. The depth of the seabed may be, forexample, from 50 meters to several thousand meters, with a depth of afew hundred meters being typical. The actual sampler is provided in ahousing 1 with a top cover 2 and a bottom cover 3 and is arranged toreceive a through-going tool 4, which in FIG. 1 is a sampler tube or asection of a sampler tube.

In the housing 1 there are provided one or more low pressure chambers 5with a pressure which is lower than the pressure in the surroundingwater. The hydrostatic penetration device will be employed in sea depthswhich are greater than can easily be reached from the surface, in whichcase the surrounding water will have a pressure which will be at leastseveral bar. The low pressure chamber 5 must have a pressure which islower than this. The simplest solution is to have the low pressurechamber at a pressure of 1 bar, which can be achieved by allowing thepressure chamber to stand open to the atmosphere before placing thepenetration device on the seabed, but of course it is possible for thepressure chamber to have other pressures.

In the housing there is further provided at least one hydraulic cylinder6 with a vertically movable piston, not shown, and a piston rod 10 whichcan be operated for upward and downward movement by a flow ofpressurized water from the surrounding water to the low pressure chamber5. This flow of water is led via pipes and valves in order to controlthe piston's and thereby the piston rod's 10 movement. The pipes andvalves can be provided per se in several ways, but in the followingdescription will be illustrated and discussed in a preferred embodiment.

The piston rod 10 is connected to a vertically movable weight 7 which isprovided around the sampler tube 4. The mass of the weight 7 can beadjusted by having the weight 7 composed of several loose weights.

The piston rod 10 and the weight 7 are connected via a link arm 9 to aclamping device 8 which surrounds the tool 4. During a downwardlydirected driving phase the clamping device 8 is brought into secureengagement with the sampler tube 4, thus causing the force from thepiston rod 10 and the influence of the weight 7 to be transferred to thesampler tube 4. During an upwardly directed return phase the piston rod10 lifts the weight 7, bringing the clamping device 8 out of engagementwith the sampler tube 4, thus causing the clamping device to slideupwards along the sampler tube. At the end of the return phase a valvewhich will be discussed in more detail later is influenced, thusinitiating the piston rod's downward movement. The clamping device 8 issimilarly activated at the end of the return phase, locking on to thesampler tube 4.

The entire housing 1 can rest on the seabed and be anchored by means ofa skirt 28 which acts as a suction anchor.

FIG. 2a shows in more detail the design of the sampler in FIG. 1. Theclamping device 8 comprises at least one clamp bit 12 which is connectedto an eccentric device 13 via at least one link arm 14. When theoperation is completed, the sampler tube 4 will in fact be pulled upbefore the sampler or the housing 1, the eccentric device 13 thenreleasing the clamping device 8 when the clamping device hits the topcover 2. As illustrated in FIG. 2a, there is attached to a bracket 8 aat least one spring 15 a which holds the link arm 14 up and the clampbit 12 against a movable sleeve 16 which is provided around the samplertube 4, the sleeve 16 forming a stop for the clamp bit 12 and helping toregulate the clamping force. At least one additional spring 15 b holdsthe clamp bit 12 in contact with the sampler tube 4, the spring 15 bconnecting the eccentric device 13 with the bracket 8 a. In the surfacewhich surrounds the sampler tube 4 the clamp bit 12 may be provided witha friction coating or with a toothing device which engages with thesampler tube's surface in order to provide a secure attachment.

As mentioned, the clamping device 8 is activated when the sampler tube 4is pulled out of the housing 1. For this purpose release bodies 17 areconnected with the eccentric device 13, and when these release bodies 17hit the top cover 2, the eccentric device 13 is rotated and the clampbit 12 is pulled away from the sampler tube 4.

In the embodiment in FIG. 2a the link arm 9 is provided with a groove 9b with an upper stop 9 c and a lower stop 9 d, and the piston rod 10 andthe weight 7 are connected to the link arm 9 by a bolt 9 a which can bemoved in the groove 9 b. During the return phase the bolt abuts againstthe upper stop 9 c, thereby lifting the clamping device along the tube4. During the first part of the subsequent driving phase the bolt 9 acan move freely in the groove 9 b. The piston rod 10 and the weight 7thereby move rapidly downwards, and, if the water flows sufficientlyquickly out of the hydraulic cylinder 6, will almost achieve free fall.When the bolt 9 a meets the lower stop 9 d an impact will occur which istransferred from the link arm 9 to the clamping device 8 and the tube 4,with the result that the latter is driven down through the seabed or thebottom sediments.

Furthermore, in the embodiment in FIG. 2a there is provided in the lowerpart of the sampler housing a tubular or sleeve-shaped guide 71 for thesampler tube, which guide 71 may, e.g., be attached via a flange to thebottom plate 3.

In the variant in FIG. 2b, instead of the suction anchor 28 there areprovided, for example, two spears 29 which stabilise the housing 1,anchoring it to the seabed.

FIG. 2c illustrates a second variant of the embodiment in FIG. 1,especially intended for use at great depths. Here the link arm 9 isreplaced by a link arm 9′ which is not provided with grooves, and whichthereby connects the clamping device 8 directly with the liftingcylinder 6. In this case the free fall of the weight 7 no longer occursand the entire stroke length in the lifting cylinder 6 can be employedfor driving the sampler tube 4 down into the bottom sediments, since thehydraulic pressure from the pressure difference between the surroundingwater and the low pressure chamber is sufficiently great to drive downthe sampler tube. This embodiment is particularly advantageous when thehydrostatic penetration device is employed to drive a test probe downinto the seabed, since in this case a steady penetration speed ofapproximately 2 cm/s is required.

The embodiment in FIG. 2c is also illustrated with a safety valve 54 bfor the low pressure chamber 5. In this embodiment anchoring must beperformed with the suction anchor 28, since otherwise the sampler couldbe torn away from the seabed during the driving phase.

A second embodiment of the hydrostatic penetration device, especially ahydrostatic sampler according to the present invention, is illustratedin FIG. 3. In FIG. 3, and illustrated in more detail in FIG. 4, thesampler has a clamping device 8 which comprises at least one bracket 18,at least one clamp bit 19 in addition to a cone 20 provided between theclamp bit 19 and the bracket 18. The clamp bit 19 is provided in such amanner that it surrounds the tool or the sampler tube 4. Moreover, theclamp bit 19 and the cone 20 are axially at least partially divided upinto segments which radially surround the sampler tube 4. Around thesampler tube 4 there may be provided at least one annular disc 21 in theclamp bit 19 and between the clamp bit 19 and the cone 20 a number ofsprings 22, with the result that the annular disc 21 and the springs 22hold the clamp bit 19 together with a light pressure on the sampler tube4. There is provided at least one spring cotter 23 which localises theclamp bit 19 and the cone 20 during the return phase of the strokemovement. A movable casing 24 which constitutes a stop for the clamp bit19 helps to regulate the axial clearance of the clamp bit 19 relative tothe clamping force. The radial forces are thereby restricted during thedriving phase of the stroke movement.

In the driving phase of the stroke movement the weight 7 falls freeuntil the bolt 9 a meets the lower stop 9 d in the lower end of thegroove 9 b in the link arm 9. The bracket 18 is thereby kept pressedagainst the cone 20, which in turn presses the clamp bit 19 against thesampler tube 4.

During the return phase of the piston rod 10 the bolt 9 a abuts againstthe upper stop 9 c, thus causing the bracket 18 to be forced upwards,releasing its pressure against the cone 20. In turn the cone 20 therebyloses its pressure against the clamp bit 10, with the result that itdisengages with the sampler tube 4, and the entire clamping device 8 isreleased from the tube 4 and can be moved along it.

As shown in FIG. 4, there are connected with the cone 20 release bodies25 which, when the sampler tube 4 is withdrawn from the seabed, strike aplate 26 provided on the top of the bracket 18 around the tool 4, thuscausing the plate 26 to strike the top cover 2, and the release body 25to be pressed against a ring 27 provided on the top of the cone 20 andaround the sampler tube 4. The cone 20 is thereby pushed downwards andthe clamp bit 19 away from the sampler tube 4. The sampler tube 4 canthereby be completely withdrawn from the bottom sediment before thesampler is lifted up from the seabed. At the lower end of the samplerthe sampler tube 4 is surrounded by a guide casing 30 which is attachedto the bottom plate 3.

During the driving phase of the stroke movement the guide casing 30penetrates down into the seabed, securing and stabilising the sampler.

A more compact version of the sampler in FIG. 3 is illustrated in FIG.5. Here a chamber 101 is provided above the low pressure chamber, thusenabling the clamping device 8 to move in the chamber 101. On the topcover 2 there is provided a ring 102, thus transferring the impactenergy in the driving phase of the stroke movement from the ring 102 tothe clamping device 8. For uncoupling of the clamp bit 19 there areprovided release bodies at the top of the lifting cylinder 6. Theserelease bodies comprise a pin 103, a bracket 104, a casing 105 andrelease bolts 106. The pin 103 can move freely until the ring 102strikes the bracket 104. This presses the casings 105 against therelease bolts 106, thereby uncoupling the clamp bit 19 and permittingthe sampler tube 4 to be withdrawn from the seabed. To prevent foreignobjects from penetrating the sampler, i.e. between the low pressurechamber 5 and the bottom cover 3, the sampler casing is surrounded by abasket 100. As shown in FIGS. 6a and 6 b, in this version the sampler isequipped with a valve 52 attached on a valve holder 52 a. This valveforms part of a valve arrangement 107 which is attached to the liftingcylinder 6 and is controlled by telescopic cylinders 108. This valvearrangement 107 constitutes a variant of the valve control for thehydrostatic penetration device or the sampler according to theinvention, the valve control being discussed in more detail withreference to FIGS. 7, 8 and 9.

FIG. 7 illustrates an embodiment of the penetration device where thecylinder volume above the piston in the hydraulic cylinder 6 ispermanently connected to the low pressure chamber 5 via a pipe 31, whilethe cylinder volume below the piston is connected via a pipe 33 to avalve 32. The valve 32 is connected to the low pressure chamber 5 by apipe 34, and to the surrounding water by a pipe 35, a valve 36 and afilter 37. The valve 36 can be opened and closed by a rocker arm 38 toprevent the stroke movement during raising and lowering of the sampler.The cylinder volume below the piston in the hydraulic-cylinder 6 can beconnected via the valve 32 alternately to the low pressure chamber 5 andthe surrounding water.

The housing 1 has at least one opening to the surrounding water (notshown), with the result that the pressure inside the housing is equal tothe ambient pressure. This causes the piston rod 10 to be exposed to theambient pressure, which results in a constant downwardly directedexternal force on the piston rod, equal to the product of the ambientpressure and the piston rod's area. In addition a constant downwardlydirected force is in action which is equal to the product of thepressure above the piston, i.e. the pressure in the low pressurechamber, and the area of the top surface of the piston.

When the cylinder volume above of the piston is connected via the valve32 to the low pressure chamber 5 an upwardly directed force is generatedwhich is equal to the product of the pressure in the low pressurechamber and the area of the bottom of the piston. Since the ambientpressure at those depths in which the hydrostatic penetration devicewill be employed is much greater than the pressure in the low pressurechamber, this upwardly directed force will be less than the sum of thetwo downwardly directed forces, with the result that the piston will bemoved downwards.

When the cylinder volume below of the piston is connected via the valve32 to the surrounding water, an upwardly directed force is generatedwhich is equal to the product of the ambient pressure and the area ofthe bottom surface of the piston. Applying the same reasoning as above,this force will be greater than the sum of the two downwardly directedforces with the result that the piston will be moved upwards.

The magnitude of the forces will depend on the dimensioning, but withthe ambient pressures which prevail at the depths concerned, the pistonrod can be made to move in both directions with great force.

This method of control permits the piston rod to be moved in bothdirections by merely allowing one side of the piston to be exposed tovarying pressure. This kind of control is highly advantageous on theseabed, permitting an automated control without the use of electronics.

As illustrated in FIG. 8, the valve 32 comprises a valve housing 39 andhas a slide 40 with a piston 41 at one end and is guided in a chamber 42in the valve housing 39 by a one-way valve 43. The one-way valve 43provides free movement of the water in one direction, but blocks thewater's movement in the opposite direction. The water's movement in thisopposite direction is reduced by a choke 44. A spring 45 attempts toforce the piston 41 to push water out through the choke 44, the choke 44thereby regulating the speed of the slide 40 in its upwardly directedmovement.

The slide 40 is arranged to be influenced by a slide 46 which isoperated by a spring 47 and is regulated via a choke 48, the slide 46being provided in a housing 49 and moving therein. The housing 49 isequipped with a one-way valve 50 which provides free return when an arm51 which is operated by the weight 7 lifts the slide 45 and extends thespring 47.

When the driving phase or drop stroke is over, the return phase orreturn stroke begins, the choke 48 and the valve 50 ensuring that thereturn stroke does not start until a predetermined period has elapsed.This may be relevant when, e.g., a sample has to be taken ofparticularly hard sediments, with the result that the sampler does nothave sufficient energy in the drop stroke to move the piston rod all theway down, i.e. to utilise the whole stroke length. The time control ofthe valve in the valve housing 49 ensures, for example, that the returnstroke or the return phase can begin even though, e.g., the drop strokeonly comprises a quarter of the possible stroke length. In the returnstroke the valve 32 opens to the pipe 35 and on to the pipe 33, thuscausing the hydraulic cylinder 6 to start the return phase of the strokemovement and lift the weight 7, the clamping device 8 now of coursebeing uncoupled from the sampler tube 4. The valve chamber 42 or thevalve 32 is connected to the low pressure chamber 5 via the pipe 34 andis evacuated after the end of the return stroke thereto, thus enablingthe driving phase or the drop stroke to start again.

The valve 36 in FIG. 7 also corresponds to the valve 52 in FIGS. 6a and6 b. The valve 36 or 52 ensures that the stroke movement does not startuntil the sampler reaches the bottom.

FIG. 9 illustrates a slightly divergent design of the valve controlshown in FIG. 7 and FIG. 8. Here the chamber 42 in the valve housing 39is designed with an increase in the diameter of its lower part, with theresult that, after a slow introductory movement, the piston 41 movesmore rapidly.

When hauling up the hydrostatic sampler the line 53 is drawn tight asshown in FIG. 7, thus opening the valve 54 a to the suction anchor 28,if this is provided, with the result that a pressure equalisation isobtained when the sampler is pulled up. Similarly, the low pressurechamber 5 may be equipped with a valve 54 b, see FIG. 2c, which ensurespressure equalisation in the low pressure chamber during the pulling upoperation.

Before the hydrostatic sampler according to the invention is pulled up,the sampler tube 4 is withdrawn from the sediment and locked in thewithdrawn position. The entire sampler can then be hauled up, forexample, by means of devices which are illustrated in FIG. 3. Here thetop of the sampler tube 4 is attached to a head 67 which is attached bymeans of a bolt 68 to a swivel housing 62. Wires 66 connect the swivelhousing 62 to eyebolts 65 on the top cover 2 of the sampler, and theeyebolts 65 are connected via stays 64 a to the low pressure chamber 5for raising and lowering of the sampler. In the swivel housing 62 thereis mounted a swivel shaft 62 a, the swivel shaft 62 a being locked to alift eye 69 for attachment of a tricing line which can run between atower at the top of the sampler, the tower being composed of sectionswhich have a length which at least corresponds to a sampler tube, thisbeing discussed in more detail with reference to FIG. 17. The top of thetower thus forms a carrier for the swivel housing 62 in order to liftthe sampler into a vertical position. The sampler housing 1 may beequipped with a number of fastening means on the side, thus enabling theentire sampler and the tower to be lifted into a horizontal position,while at the same time the tower constitutes a support for the tool orthe sampler tube 4.

As illustrated in FIGS. 10a and 10 b, the hydrostatic penetration deviceaccording to the invention can also be employed as a passive test probefor a “cone penetration test” (CPT). For this purpose the piston rod 10is attached to the bracket 18 without the use of link arms. The clampbit 19 and the head 67 are adapted to the CPT probe. On the return pipe34 to the low pressure chamber 5 there is provided a flow control valve63 in order to attain constant stroke speed. Otherwise the embodimentmay be similar to the embodiment in FIG. 3.

FIG. 11 illustrates an embodiment where the housing including the lowpressure chamber is employed as extra stroke weight. Here the hydrauliccylinder 6 is attached at its lower end to the bottom cover 3, which inthis design is movable in relation to the rest of the housing 1. Thepiston rod 10 is attached to the housing 1 and the low pressure chamber5. The link arm 9 is attached to the low pressure chamber at the lowerend and to the bracket 18 at its upper end. The stays 64 b act as aguide between the low pressure chamber 5 and the bottom cover 3. Thusduring a downwardly directed movement of the piston rod 10 both thehousing I and the low pressure chamber 5 will contribute to thedownwardly directed force with their weight. In addition to the factthat the inertia of the mass of the housing and the low pressure chambertransfer an impact to the tool or the tube, the mass of the water whichis located inside the housing and the low pressure chamber willcontribute to the impact with its inertia. Otherwise the functions aresimilar to those in the embodiment in FIG. 3.

A preferred embodiment of the sampler according to the invention isillustrated in FIG. 12a in sectional elevation and FIG. 12b in crosssection. In FIG. 12a the return spring 47 (FIG. 8) is reinforced by aweight 70. The low pressure chamber is provided in the form of a numberof cylinders 5 around the sampler tube 4, as shown in FIG. 12b, whereeight low pressure chambers 5 are illustrated. In the embodiment in FIG.12 a filter is realised in a special manner and indicated by 37 in FIG.12b.

FIGS. 13 and 14 illustrate an alternative embodiment of the hydrostaticpenetration device according to the invention. Here the hydrauliccylinder is designed as a centrally placed cylinder 110 in the housing1. Together with an external casing 111, the top cover 2 and the bottomcover 3 the hydraulic cylinder 110 defines the low pressure chamber 5.The weight and the piston rod are composed of a cylinder 112 providedinside the hydraulic cylinder 110, and the piston is composed ofdiametrical gradations of the piston rod 112, the diametrical gradationsof the piston rod 112 together with corresponding gradations of thehydraulic cylinder 110 and the walls of the hydraulic cylinder and thepiston rod defining variable cylinder volumes. The tool 4 is conveyed inguides 113 along the piston rod's 112 centre line, and the clampingdevice 8 is attached in the piston rod 112.

A first variable cylinder volume 120 is permanently connected to the lowpressure chamber 5 via an outlet 127. The piston in this first variablecylinder volume 120 is composed of a first diametrical gradation 122 ofthe piston rod 112. A second variable cylinder volume 121 is alternatelyconnected to the low pressure chamber 5 and the surrounding water via anoutlet 124 which is connected to valves 115 and 116. The piston in thissecond variable cylinder volume 121 is composed of a second diametricalgradation 123 of the piston rod 112. The first and second gradations arearranged in such a manner that the first variable cylinder volume 120decreases when the second variable cylinder volume 121 increases, andvice versa. This is achieved by having the first and second gradationsoppositely directed, with the result that a pressure on the firstdiametrical gradation 122 will attempt to force the piston rod 112downwards, while a pressure on the second diametrical gradation 123 willattempt to force the piston rod upwards.

The first diametrical gradation 122 forms a piston surface with a firstcross section, and the second diametrical gradation 123 forms a pistonsurface with a second cross section which is larger than the first crosssection. By this means the same advantageous control is obtained of thepiston rod's movement as was described in connection with FIG. 7.

In order to control the connection between the second variable cylindervolume 121 and the low pressure chamber 5 and the surrounding waterrespectively, the control of the valves 115 and 116 is performed bymeans of impulses from impulse couplings 125 and 126 from the second andfirst variable cylinder volumes respectively. The impulse from the firstcylinder volume 120 occurs when the piston rod 112 has moved to itsupper position, see FIG. 13, with the result that the gradation 122blocks the outlet 127 from the first cylinder volume. Remaining fluidwhich is located in the first cylinder volume will thereby becompressed, giving an impulse through the impulse coupling 126. Thisimpulse is used to control the valves 115 and 116, which is prior artand will not be described further, thus connecting the outlet 124 of thesecond cylinder volume 121 to the low pressure chamber 5. This causesthe piston rod to move downwards to its lower position during itsdriving phase, see FIG. 14, where the second diametrical gradation 123blocks the outlet 124. Remaining fluid which is located in the secondcylinder volume will thereby be compressed, giving an impulse throughthe impulse coupling 125. This impulse causes the valves 115 and 116 toconnect the second variable cylinder volume 121 to the surroundingwater, thus moving the piston rod upwards. In addition to thesurrounding water being supplied through the outlet 124, it is alsosupplied through the impulse coupling 125, since the outlet 124 isclosed by the second diametrical gradation 123 when the piston rod 112is located in its lower position.

In connection with FIG. 15 a special tool will now be described for usewith the invention, namely a sampler tube 4 at the lower end of which isprovided a head 55 with two closing jaws 56 hinged to the head with asubstantially tubular cross section and toothed gripping surfaces whichsynchronise the closing jaw's movement. The hinging is provided by a pin57. When the sampler tube 4 is withdrawn from the bottom sediment, thebore core is cut by the closing jaws 5 b and held in the sampler tube 4while pulling up is in progress.

In a second embodiment illustrated in FIG. 16 the tool is similarly asampler tube 4, but equipped with a valve, with the result that in thesampler tube there is created an underpressure which sucks up the borecore. This is a so-called “piston corer”. In this embodiment the samplertube 4 has a head 58 provided at its lower end in the form of a valvehousing with a valve plate 59 and an arm 60 which constitutes a one-wayvalve which in an open position admits water through the sampler tube 4,thus permitting water inside the tube to flow upwards during the tube'sdownwardly directed movement. The valve is attached via the line 61 to,e.g., the top of a tower.

FIG. 17 shows a double tower 130 consisting of a shaft or a course 131for a sampler tube with swivel, and a corresponding course 132 for atool for a test probe for measuring mechanical or electrical resistancein the seabed. The lower end of the tower 130 is attached to twohousings 135, 136 for hydrostatic penetration devices for the samplerand the tool for the test probe respectively. A wire 138 runs via ablock 137 between a sampler tube 133 and a test probe 134. The courses131, 132 have lengths which correspond to the lengths of the respectivepenetration tubes or tools, thus enabling the penetration tubes to bepulled up into the tower. The sampler tube 133 is pulled up in thecourse 131, and the test probe 134 is pulled up in the course 132. Thetower 130 can be lifted aboard a vessel by means of a lifting wire whichis attached in the block 137.

With a hydrostatic penetration device or sampler according to thepresent invention it is possible to employ tools and sampler tubes withdifferent diameters, and in this case parts of the clamping device 8,including the clamp bit 12, 19 together with the guide casing 71 have tobe replaced by similar components adapted to the tool's altereddiameter. In the embodiment in FIG. 1, e.g., the link arm 14 and thecasing 16 also have to be replaced and in the embodiment in FIG. 3 thecasing 24 and possibly the plate 26.

The hydrostatic penetration device according to the present invention ispreferably operated from a vessel, in which case replacement of tools orsampler tubes is performed on board the vessel after the penetrationdevice or the sampler has been hauled up. If, e.g., a sampler isemployed to take a core sample of sediments on the seabed, the sampleris hauled up for extraction of the core sample from the sampler tube 4on board the vessel. This operation does not form part of the invention,and is therefore not shown in any of the figures, but nevertheless itwill be described briefly with reference to FIG. 5 in order to exemplifythe use of tools in the form of sampler tubes as illustrated in FIG. 15.After the sampler has been hauled up into the vessel, the head 55 isscrewed off the sampler tube 4. The bolt 68 is then removed from theswivel housing 62 on the top of the sampler tube and the swivel housing62 is removed. A piston 67 b is inserted in the cylindrical head 67. Arear seal 67 c is then mounted with the bolt 68 as locking. Water underpressure is pumped into a connection 67 d, forcing the piston 67 bagainst a liner 4 b which is a plastic tube which is located inside thesampler tube 4, surrounding the seabed sample. The liner 4 b with theseabed sample is then expelled from the sampler tube 4 for subsequentcutting and sealing.

Even though the hydrostatic penetration device with associated tools isillustrated and described in the above as a hydrostatic sampler, anumber of variants may be realised both of the hydrostatic penetrationdevice and the tools employed therein for a variety of purposes andwithin the scope of the present invention. The described embodimentsshould therefore by no means be considered as limiting for theinvention.

What is claimed is:
 1. A hydrostatic penetration device for placing onand penetration of the seabed, comprising a housing (1) with a top cover(2) and a bottom cover (3), and a through-going vertical tool (4) forpenetration of the seabed, characterized in that it comprises: at leastone low pressure chamber (5) with a pressure which is lower than thepressure in the surrounding water, at least one hydraulic cylinder (6)with a vertically movable piston and piston rod (10) which can beoperated for an upward and downward movement by a flow of pressurisedwater from the surrounding water to the low pressure chamber (5), pipesand valves for leading and controlling said flow of pressurised water,for control of the piston's and thereby the piston rod's (10) movement,a clamping device (8) which surrounds the tool (4) and is connected tothe piston rod (10), and which by means of an upward and downwardmovement of the piston rod can be brought out of and into engagementwith the tool respectively, at least one vertically movable weight (7)connected to the piston rod, arranged to transfer its weight to theclamping device (8) during a downward movement, whereby during an upwardmovement the piston rod (10) will lift the weight (7) and bring theclamping device (8) out of engagement with the tool (4), thus causingthe clamping device to slide upwards along the tool, and during asubsequent downward movement will bring the clamping device (8) intoengagement with the tool (4), with the result that under the influenceof the weight (7) and force from the piston rod (10) the tool is drivendown into the seabed.
 2. A hydrostatic penetration device according toclaim 1, characterized in that the cylinder volume above the piston inthe hydraulic cylinder (6) is permanently connected to the low pressurechamber (5), that the cylinder volume below the piston during the pistonrod's (10) upward and downward movement is connected to the surroundingwater and the low pressure chamber (5) respectively, and that thehousing (1) has at least one opening to the surrounding water, thuscausing the piston rod to be exposed to the pressure in the surroundingwater.
 3. A hydrostatic penetration device according to claim 1,characterized in that the clamping device (8) comprises clamp bits (12)which are clamped by spring-loaded link arms (14) against the tool (4),and that the link arms (14) are connected, possibly via connecting links(9, 13, 8 a), to the piston rod (10), in order to pull the clamp bits(12) away from the tool when the piston rod is located in its upperposition.
 4. A hydrostatic penetration device according to claim 1,characterized in that the clamping device (8) comprises at least oneconical clamp bit (19) which is at least partially divided up into axialsegments and arranged around the tool (4), at least one cone (20) whichis at least partially divided up into axial segments and arrangedoutside the clamp bit (19), both the clamp bit (19) and the cone (20)extending downwards, and at least one bracket (18) arranged outside thecone and connected to the piston rod (10) and which during a downwardlydirected movement of the piston rod (10) is caused to clamp the cone(20) against the clamp bit (19), with the result that the clampingdevice (8) is locked to the tool (4).
 5. A hydrostatic penetrationdevice according to claim 4, characterized in that around the tool (4)there is provided at least one annular disc (21) in the clamp bit (19)and between the clamp bit (19) and the cone (20) a number of springs(22), with the result that the annular disc (21) and the springs (22)hold the clamp bit (19) together with a light pressure against the tool(4).
 6. A hydrostatic penetration device according to claim 1,characterized in that the piston rod (10) and the weight (7) aremutually axially secured, while at the same time they are axiallymovably (9 b) connected to the clamping device (8) with an upper stop (9c) and lower stop (9 d), with the result that during an upwardlydirected movement the piston rod (10) and the weight (7) will abutagainst the upper stop (9 c), bringing the clamping device (8) out ofengagement with the tool (4), and during a downwardly directed movementwill leave the upper stop, with the result that the clamping device (8)is moved into engagement, after which it drops to the lower stop (9 d),thus causing an impact to be transferred to the clamping device and thetool.
 7. A hydrostatic penetration device according to claim 1,characterized in that release bodies (17, 25) for the clamping device(8) are connected to the top cover (2), with the result that when thetool (4) is pulled up, thus moving the clamping device towards the topcover (2), the clamping device (8) will be brought out of engagementwith the tool (4).
 8. A hydrostatic penetration device according toclaim 1, characterized in that hoses or pipes from the cylinder volumebelow the piston in the hydraulic cylinder (6) are passed to a valve(32) which in turn is connected to the low pressure chamber (5) and thesurrounding water, and that the valve (32) is provided with apretensioning device (47, 70) which presses the valve into a positionwhere the connection to the low pressure chamber (5) is closed and theconnection between the cylinder volume below the piston in the hydrauliccylinder (6) and the surrounding water is open, thus causing the pistonand the piston rod (10) to be moved upwards.
 9. A hydrostaticpenetration device according to claim 8, characterized in that an arm(51), which is securely connected to the weight (7) or the piston rod(10), is arranged in such a manner that, when the piston rod (10) islocated in its upper position, it overrules the pretensioning device(47, 70) and steers the valve (32) to a position where the connection tothe surrounding water is closed and the connection between the cylindervolume below the piston and the low pressure chamber (5) is open, thuscausing the piston and the piston rod (10) to be moved downwards.
 10. Ahydrostatic penetration device according to claim 9, characterized inthat the valve (32) is provided with a time delay device which delaysits movement towards the position where the connection to the lowpressure chamber (5) is closed and the connection between the cylindervolume below the piston in the hydraulic cylinder (6) and thesurrounding water is open.
 11. A hydrostatic penetration deviceaccording to claim 10, characterized in that the time delay device iscomposed of a slide (46) which moves in a housing (49) and which isimpelled by a spring (47) to force water out of the valve housing (49)through a choke (48), and a one-way valve (50) which admits water intothe housing (49) when, under the influence of the arm (51), the slide ismoved in the opposite direction.
 12. A hydrostatic penetration deviceaccording to claim 8, characterized in that the valve (32) comprises avalve housing (39) with a slide (40) which has a piston (41) which isoperated by a spring (45) at one end and which in a chamber (42) in thevalve housing (39) is controlled by a one-way valve (43) which providesa free movement of the water in one direction, and a choke (44) whichchokes the movement of the water in the opposite direction.
 13. Ahydrostatic penetration device according to claim 1, characterized inthat an arm (38) or plate (26) which is securely connected to theclamping device (8) is arranged to close a valve (36, 52) for intake ofsurrounding water to the hydraulic cylinder (6) when the clamping device(8), during a phase where the housing (1) is suspended in the tool (4),has been pulled up towards the top cover (2).
 14. A hydrostaticpenetration device according to claim 1, characterized in that thebottom of the bottom cover (3) is provided with a suction anchor (28)for attachment to the seabed.
 15. A hydrostatic penetration deviceaccording to claim 1, characterized in that the bottom of the bottomcover (3) is provided with at least one spear (29) for attachment to theseabed.
 16. A hydrostatic penetration device according to claim 1,characterized in that the bottom cover (3) is provided verticallymovable in relation to the housing (1) and attached to the hydrauliccylinder (6), and that the housing (1) and the low pressure chamber (5)are attached to the piston rod (10), whereby the housing (1), the lowpressure chamber (5) and water which is located in the housing willsupply the clamping device (8) and the tool (4) with percussive energyduring the piston rod's downwardly directed movement.
 17. A hydrostaticpenetration device according to claim 1, characterized in that thehydraulic cylinder is designed as a centrally located cylinder ( 10) inthe housing (1) and together with an external casing (111), the topcover (2) and the bottom cover (3) define the low pressure chamber (5),that the weight and the piston rod are composed of a cylinder (112)provided inside the hydraulic cylinder (110), that the piston iscomposed of diametrical gradations of the piston rod (112), thediametrical gradations of the piston rod (112) together withcorresponding gradations of the hydraulic cylinder (110) and the wallsof the hydraulic cylinder and the piston rod defining variable cylindervolumes, that the tool (4) is passed in guides (113) along the pistonrod's (112) centre line, and that the clamping device (8) is attached tothe piston rod (112).
 18. A hydrostatic penetration device according toclaim 17, characterized in that a first variable cylinder volume (120)is permanently connected to the low pressure chamber (5) and that inthis first variable cylinder volume (120) the piston is composed of afirst diametrical gradation (122) of the piston rod (112) with a firstcross section, that a second variable cylinder volume (121) isalternately connected with the low pressure chamber (5) and thesurrounding water, and that in this second variable cylinder volume(121) the piston is composed of a second diametrical gradation (123) ofthe piston rod (112) with a second cross section which is larger thanthe first cross section, and that the first and second gradations arearranged in such a manner that the first variable cylinder volume (120)decreases when the second variable cylinder volume (121) increases, andvice versa.
 19. A tool for use with a hydrostatic penetration deviceaccording to claim 1, especially a sampler for core samples, where thetool (4) is a sampler tube, characterized in that the sampler tube (4)has provided at its lower end a head (55) with two closing jaws (56)hinged to the head with substantially tubular cross section and toothedgripping surfaces which synchronise the closing jaws' movement.
 20. Atool for use with a hydrostatic penetration device according to claim 1,especially a sampler for core samples, where the tool (4) is a samplertube, characterized in that the sampler tube (4) has provided at itslower end a head (58) in the form of a valve housing with a valve plate(59) and an arm (60) which constitutes a one-way valve which in an openposition admits water into the sampler tube (4).